The traditional tube used in the collection and processing of biological samples has been the glass test tube, and variations thereof.
The brittleness of glass, together with its general weakness, a tendency to shatter, and to form dangerous cutting surfaces when broken, as well as its non combustibility have militated against its use.
These disadvantages of glass are particularly emphasized in relation to the handling of blood samples wherein a retro-virus such as HIV-manifesting or the AIDS virus, or other infectious or hazardous substances may be present.
Thus, the use of a potentially shatterable tube for collection and transportation of potentially highly infectious and hazardous substances is evidently undesirable, while the sharpness of its shards with their inherent capacity to wound and infect makes continuing use thereof untenable.
The adoption of plastic tubes for purposes of blood separation, by way of coagulation, and separation of serum by centrifugal separation is taught by U.S. Pat. No. 4,856,533 granted Aug. 15th, 1989.
In the case of tubes for use in blood analysis work a group of surface active coatings exists including, Ethylenediaminetetraacetate (E.D.T.A.), finely divided silica gel, silica, sodium heparin, silicon and its modifications, potassium oxalate, sodium chloride, sodium citrate, citric acid, kaolin.
However, the gas sealing capability of these materials is quite limited, when considered in relation to glass, as an illustrative standard. Furthermore, particularly in the case of acrylonotrile group of resins, these are peculiarly inappropriate for the proposed usage as they form cyanide gas when incinerated, and are thus unsuited to incineration.
The need to provide safe incineration when disposing of blood samples possible containing the AIDS virus or infectious substances together with the contaminated tube, evidently requires no argument.
The above-identified document teaches also the need for the use of a hydrophilic surface coating on the interior of the collection tube, to preclude adhesion of a blood clot to the tube walls due to the existence of an undue number of blood coagulation sites on the plastic surface.
Use of inorganic adsorptive substances such as glass, silica, kaolin, cerite etc., is combined with a water soluble substance and an adsorptive inorganic substance to achieve coagulation in a controlled fashion. The examples taught comprise modified aliphatic silicone oils, modified aromatic silicone oils, modified paraffin, modified wax, etc., for which a number of examples are given.
Examples of water soluble substances that are given comprise low molecular weight and high molecular weight substances, particularly intended for blood fraction separation.